1. Field of the Invention
This invention relates generally to pressure fluctuating tools used in well bores, and specifically to an improved downhole pressure fluctuating feedback system that regulates the frequency of oscillation of a downhole oscillator.
2. Description of the Prior Art
It is known in the art to provide pressure variations in the drilling fluid to enhance the drilling rate. Edward M. Galle, et al, U.S. Pat. No. 3,405,770 discloses a system whereby a well bore oscillator is used to provide pressure fluctuations in the drilling fluid. A feedback system is provided to regulate the frequency of oscillation. In Edward M. Galle, et al, the feedback system comprises two compliance cavities that are formed by drilling two holes parallel to the axial bore of the tubular member which carries the oscillator assembly. These two compliance cavities are connected to the output legs of the oscillator and to the feedback nozzles of the oscillator by way of four inertance passageways.
Edward M. Galle, et al. U.S. Pat. No. 4,630,689, discloses an improvement to U.S. Pat. No. 3,405,770. In this improvement, the compliance cavities in the body of the tubular member in U.S. Pat. No. 3,405,770 are replaced by a pair of U-shaped tubes. However, these tubes are subject to fatigue failures.